Reversible electrodeposition devices and associated electrochemical media

ABSTRACT

The present invention is directed to a reversible electrodeposition device comprising: a first substrate having an electrically conductive material associated therewith; a second substrate having an electrically conductive material associated therewith; a nucleation layer at least partially covering at least one of the electrically conductive materials of the first and second substrates; an electrochemical medium contained within a chamber positioned between the first and second substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S.application Ser. No. 10/681,538, filed Oct. 8, 2003, which is herebyincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to electrochemical devices,and, more particularly, to reversible electrodeposition devices havingelectrochemical media which serve to enhance both durability andreversible deposition uniformity of the electrodeposition devicesrelative to the same without such electrochemical media.

2. Background Art

Electrodeposition devices have been known in the art for several yearsand are the subject of a plurality of United States patents, including,for example, U.S. Pat. No. 5,056,899 entitled “Material For LightModulation and Manufacturing Processes,” U.S. Pat. No. 5,903,382entitled “Electrodeposition Cell With High Light Transmission,” U.S.Pat. No. 5,923,456 entitled “Reversible Electrochemical Mirror,” U.S.Pat. No. 6,111,685 entitled “Reversible Electrochemical Mirror (REM)With Improved Electrolytic Solution,” and U.S. Pat. No. 6,166,847entitled “Reversible Electrochemical Mirror For Modulation Of ReflectedRadiation,”—just to name a few.

Generally, electrodeposition devices can be categorized into two groups,namely: “rocking chair” type electrodeposition devices whereindeposition/plating occurs via a plating-solution-plating mechanism (e.g.U.S. Pat. No. 5,903,382), and electrodeposition devices whereindeposition takes place while oxidation of a halide occurs at the anode(e.g. U.S. Pat. No. 5,056,899). While the above-identifiedelectrodeposition devices have been known in the art for years,operational limitations and device configurations remain largelyproblematic, or at least, less than desirable for commercialapplications.

For example, some electrodeposition devices can be susceptible todendrite formation at or near an electrode, which, in turn, canadversely affect the electrochemical performance of the device, and insome circumstances render the electrodeposition device inoperable—evenafter only relatively few cycles (i.e. a transition from a hightransmission state to a low transmission state). Moreover, several ofthe “rocking chair” type electrodeposition devices incorporate speciallyconfigured anodes which are distributed in localized, patterned areasand/or utilize a specially modified cathode as is disclosed in U.S. Pat.No. 5,923,456. Such configurations can materially increase manufacturingcomplexity, as well as compromise optical performance due to gridlines,dots, etcetera.

Electrodeposition devices as disclosed in U.S. Pat. No. 5,056,899 sufferfrom numerous drawbacks, the details of which are well disclosed in U.S.Pat. No. 5,903,382 and related cases.

It has now been surprisingly discovered that electrodeposition devicescan be fabricated which exhibit enhanced durability by controllablyselecting concentrations of anodic and/or cathodic materials within theelectrochemical media without such complex device configurations. It hasalso been surprisingly discovered that incorporating redox buffers intothe electrochemical media further enhances the electrochemicalperformance of such electrodeposition devices. (See, for example, U.S.Pat. No. 6,188,505; U.S. Pat. No. 6,310,714; and U.S. Pat. No.6,433,914—all of which are hereby incorporated herein by reference intheir entirety).

It is therefore an object of the present invention to provide anelectrodeposition device having an electrochemical medium that remediesthe aforementioned detriments and/or complications associated withconventional electrodeposition devices.

These and other objectives of the present invention will become apparentin light of the present specification, claims, and drawings.

SUMMARY OF THE INVENTION

The present invention is directed to a reversible electrodepositiondevice, comprising: (a) a first substrate having an electricallyconductive material associated therewith; (b) a second substrate havingan electrically conductive material associated therewith; (c) anucleation layer at least partially covering at least one of theelectrically conductive materials of the first and second substrates;(d) an electrochemical medium contained within a chamber positionedbetween the first and second substrates which comprises: (1) an anodicelectroactive material; and (2) cathodic electroactive material; and (e)means associated with the electrochemical medium which enhances theelectrochemical performance of the electrodeposition device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the drawingswherein:

FIG. 1 of the drawings is a cross-sectional schematic representation ofan electrodeposition device fabricated in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and to FIG. 1 in particular, across-sectional schematic representation of electrodeposition device 100is shown, which generally comprises first substrate 112 having frontsurface 112A and rear surface 112B, second substrate 114 having frontsurface 114A and rear surface 114B, and chamber 116 for containingelectrochemical medium 124. It will be understood that electrodepositiondevice 100 may comprise, for illustrative purposes only, a mirror, awindow, a display device, a variable reflector, and the like. It will befurther understood that FIG. 1 is merely a schematic representation ofelectrodeposition device 100. As such, some of the components have beendistorted from their actual scale for pictorial clarity. Indeed,numerous other device configurations are contemplated for use, includingthose disclosed in U.S. Pat. No. 5,056,899 entitled “Material For LightModulation and Manufacturing Processes,” U.S. Pat. No. 5,903,382entitled “Electrodeposition Cell With High Light Transmission,” U.S.Pat. No. 5,923,456 entitled “Reversible Electrochemical Mirror,” U.S.Pat. No. 6,111,685 entitled “Reversible Electrochemical Mirror (REM)With Improved Electrolytic Solution,” and U.S. Pat. No. 6,166,847entitled “Reversible Electrochemical Mirror For Modulation Of ReflectedRadiation,” all of which are hereby incorporated herein by reference intheir entirety.

First substrate 112 may be fabricated from any one of a number ofmaterials that are transparent or substantially transparent in thevisible region of the electromagnetic spectrum, such as, for example,borosilicate glass, soda lime glass, float glass, natural and syntheticpolymeric resins, plastics, and/or composites including Topas®, which iscommercially available from Ticona of Summit, N.J. First substrate 112is preferably fabricated from a sheet of glass having a thicknessranging from approximately 0.5 millimeters (mm) to approximately 12.7mm. Of course, the thickness of the substrate will depend largely uponthe particular application of the electrodeposition device. Whileparticular substrate materials have been disclosed, for illustrativepurposes only, it will be understood that numerous other substratematerials are likewise contemplated for use—so long as the materialsexhibit appropriate physical properties, such as strength, to be able tooperate effectively in conditions of intended use. Indeed,electrodeposition devices in accordance with the present invention canbe, during normal operation, exposed to extreme temperature variation aswell as substantial UV radiation, emanating primarily from the sun. Itwill be further understood that substrate 112 may be modified bytexturing either one of surfaces 112A or 112B, for example, by acidetching to form a diffusely reflecting device as is taught in U.S. Pat.No. 6,256,135 entitled “Diffusely-reflecting Reversible ElectrochemicalMirror,” which is hereby incorporated herein by reference in itsentirety.

Second substrate 114 may be fabricated from similar materials as that offirst substrate 112. Second substrate 114 is preferably fabricated froma sheet of glass having a thickness ranging from approximately 0.5 mm toapproximately 12.7 mm. If first and second substrates 112 and 114,respectively, are fabricated from sheets of glass, then the glass canoptionally be tempered, heat strengthened, and/or chemicallystrengthened, prior to or subsequent to being coated with layers ofelectrically conductive material (118 and 120).

One or more layers of electrically conductive material 118 areassociated with rear surface 112B of first substrate 112. These layersserve as an electrode for the electrodeposition device. Electricallyconductive material 118 is desirably a material that: (a) issubstantially transparent in the visible region of the electromagneticspectrum; (b) bonds reasonably well to first substrate 112; (c)maintains this bond when associated with a sealing member; (d) isgenerally resistant to corrosion from materials contained within theelectrodeposition device or the atmosphere; and (e) exhibits minimaldiffuse or specular reflectance as well as sufficient electricalconductance. It is contemplated that electrically conductive material118 may be fabricated from fluorine doped tin oxide (FTO), for exampleTEC glass, which is commercially available from Libbey Owens-Ford-Co.,of Toledo, Ohio, indium/tin oxide (ITO), doped zinc oxide or any one ofa number of other materials known to those having ordinary skill in theart.

One or more nucleation layers 119 at least partially cover the innersurface, proximate chamber 116, of electrically conductive material 118.It will be understood that regardless of its ordinary meaning, the term“nucleation layer” will be defined herein as a layer of material that atleast partially covers the inner surface proximate chamber 116 to reducethe overpotential for deposition and/or provide cathodic materialsundergoing reduction with nucleation sites, to, in turn, enhance theuniformity of correspondingly deposited films.

Nucleation layer 119 may be fabricated from any one of a number ofmaterials, including, but not limited to, transition metals, such as,gold, platinum, ruthenium, rhodium, palladium, chromium, nickel,tantalum, etcetera, and alloys thereof. Preferably, nucleation layer 119ranges in thickness from approximately 5 angstroms to approximately 100angstroms, and more preferably between approximately 10 angstroms andapproximately 50 angstroms.

Electrically conductive material 120 is preferably associated with frontsurface 114A of second substrate 114, and is operatively bonded toeither electrically conductive material 118 or nucleation layer 119 bysealing member 122. As can be seen in FIG. 1, once bonded, sealingmember 122 and the juxtaposed portions of electrically conductivematerial 118 or nucleation layer 119 and electrically conductivematerial 120 serve to define an inner peripheral geometry of chamber116. Electrically conductive material 120 may be fabricated from similarmaterials as that of electrically conductive material 118.

Sealing member 122 may comprise any material that is capable of beingadhesively bonded to the electrically conductive material 118 ornucleation layer 119 and electrically conductive material 120 to, inturn, seal chamber 116 so that electrochemical medium 124 does notinadvertently leak out of the chamber. As is shown in dashed lines inFIG. 1, it is also contemplated that the sealing member extend all theway to rear surface 112B and front surface 114A of their respectivesubstrates. In such an embodiment, the layers of electrically conductivematerial 118 and 120 and nucleation layer 119 may be partially removedwhere the sealing member 122 is positioned. If electrically conductivematerials 118 and 120 are not associated with their respectivesubstrates, then sealing member 122 preferably bonds well to glass. Itwill be understood that sealing member 122 can be fabricated from anyone of a number of materials including, for example, those disclosed inU.S. Pat. No. 4,297,401 entitled “Liquid Crystal Display AndPhotopolymerizable Sealant Therefor,” U.S. Pat. No. 4,418,102 entitled“Liquid Crystal Displays Having Improved Hermetic Seal,” U.S. Pat. No.4,695,490 entitled “Seal For Liquid Crystal Display,” U.S. Pat. No.5,596,023 entitled “Sealing Material For Liquid Crystal Display Panel,And Liquid Crystal Display Panel Using It,” U.S. Pat. No. 5,596,024entitled “Sealing Composition For Liquid Crystal,” and U.S. Pat. No.6,157,480 entitled “Seal For Electrochromic Devices,” all of which arehereby incorporated herein by reference in their entirety.

For purposes of the present disclosure, electrochemical medium 124comprises an anodic material, and a cathodic material, preferablywherein the concentration of the anodic material relative to thecathodic material is controllably selected which, as will be shownexperimentally below, serves to enhance durability and/or reversibledeposition uniformity of the electrodeposition devices relative to thesame without such controlled media concentrations.

Both of the anodic and cathodic materials are electroactive, and atleast one may be electrochromic. It will be understood that regardlessof its ordinary meaning, the term “electroactive” will be defined hereinas a material that undergoes a modification in its oxidation state uponexposure to a particular electrical potential difference. Furthermore,it will be understood that the term “electrochromic” will be definedherein, regardless of its ordinary meaning, as a material that exhibitsa change in its extinction coefficient at one or more wavelengths uponexposure to a particular electrical potential difference.

Cathodic materials may include, for example, salts of active metals suchas silver, copper, bismuth, nickel, and ligands associated with the samewhich are deposited on the nucleation layer (119) upon electrochemicalreduction. Silver is especially preferred because it is colorless in itsionic state and upon single electron reduction forms an achromic highlyreflective metallic film. While specific cathodic materials have beenprovided for illustrative purposes only, numerous other cathodicmaterials that would be known to those with ordinary skill in the arthaving the present disclosure before them are likewise contemplated foruse. It will be understood that the above-identified cathodic materialscan be incorporated in any electrochemical medium so long as the sameare capable of reduction proximate nucleation layer 119.

For purposes of the present invention, anodic materials may include anyone of a number of materials including ferrocene, substitutedferrocenes, substituted ferrocenyl salts, substituted phenazines,phenothiazine, substituted phenothiazines, triphenodithiazines,especially 3,10-dimethoxy-7,14,-(triethylammoniumbutyl)triphenodithiazine as is disclosed in U.S. Pat. No. 6,710,906, which ishereby incorporated herein be reference in its entirety, thianthrene,substituted thianthrenes, hydroquinones, and substituted hydroquinonessuch as trimethylhydroquinone. Examples of anodic materials may includedi-tert-butyl-diethylferrocene, 5,10-dimethyl-5,10-dihydrophenazine,3,7,10-trimethylphenothiazine, 2,3,7,8-tetramethoxythianthrene, and10-methylphenothiazine, as well as those provided in experiments infra.It will be understood that numerous other anodic materials arecontemplated for use including those disclosed in U.S. Pat. No.4,902,108 entitled “Single-Compartment, Self-Erasing, Solution-PhaseElectrochromic Devices, Solutions For Use Therein, And Uses Thereof,”U.S. Pat. No. 5,998,617 entitled “Electrochromic Compounds,” U.S. Pat.No. 6,188,505 B1 entitled “Color-Stabilized Electrochromic Devices,” andU.S. application Ser. No. 10/054,108 entitled “Controlled DiffusionCoefficient Electrochromic Materials For Use In Electrochromic MediumsAnd Associated Electrochromic Devices,” all of which are herebyincorporated herein by reference in their entirety. These materials mayor may not persist in solution upon electrochemical oxidation. It isalso contemplated that the anodic material may comprise a polymer film,such as polyaniline, polythiophenes, polymeric metallocenes, or a solidtransition metal oxide, including, but not limited to, oxides ofvanadium, nickel, iridium, as well as numerous heterocyclic compounds,etcetera. It will be further understood that the anodic materials may beimmobilized in a sol-gel, or via covalent and/or electrostaticattachment.

In accordance with the present invention, the anodic material may bereplaced by a counter electrode that exhibits a large capacitance. Forexample, activated carbon powders having a large specific surface areasuch as those disclosed by Nishikitani et al. (Electrochimica Acta 44,18 p3211 (1999)), which is hereby incorporated herein by reference inits entirety. Nanocrystalline doped tin oxide may also be used as acounter electrode either as an electrostatic capacitor or in combinationwith an anodic material attached thereto, as is taught in WO 01/27690,which is hereby incorporated herein by reference in its entirety.

Thus, in accordance with the present invention several methods forconstructing a device are contemplated for use, including, but notlimited to:

1. A film of poly(3,4-ethylenedioxythiophene (PEDOT). Sold under thetrade name ORGACONON on poly(ethylene terphthalate) the foil can be usedin conjunction with an electrode made from ITO on glass coated withapproximately 25 angstroms of Pt (ITO/Pt electrode) and anelectrochemical medium comprising 0.15M silver triflate (AgTf), 0.2Mtetraethyl ammonium bromide (TEABr) in DMF to assemble a device of thepresent invention. It will be understood that while a particularsubstituted polythiophene has been disclosed, for illustrative purposesonly, any one of a number of electronically or redox conducting polymerfilms/layers that would be known to those with ordinary skill in the arthaving the present disclosure before them are likewise contemplated foruse.

2. A sol-gel film made from tetraethylorthosilicate and a silanecomprising a metallocene, such as ferrocene, can be used in conjunctionwith an ITO/Pt electrode and an electrochemical medium comprising 0.15MAgTf, 0.2M TEABr in DMF to assemble a device of the present invention.It will be understood that while a particular sol-gel film has beendisclosed, for illustrative purposes only, any one of a number ofsol-gel films/layers and/or polymer films/layers that would be known tothose with ordinary skill in the art having the present disclosurebefore them are likewise contemplated for use.

3. A nanocrystalline film of SnO2:Sb with an attached electroactivemoiety can be prepared as described in WO 01/27690 and used inconjunction with an ITO/Pt electrode and an electrochemical mediumcomprising 0.15M AgTf, 0.2M TEABr in DMF to assemble a device of thepresent invention. It will be understood that while a particular surfaceattached configuration has been disclosed, for illustrative purposesonly, any one of a number of such surface attached configurations (i.e.films/layers) that would be known to those with ordinary skill in theart having the present disclosure before them are likewise contemplatedfor use.

4. A counterelectrode produced from a carbon-based paste printed viascreening or ink jet printing, for example, as is disclosed inElectrochimica Acta 44, 18 p3211 (1999)) used in conjunction with anITO/Pt electrode and an electrochemical medium comprising 0.15M AgTf,0.2M TEABr in DMF to assemble a device of the present invention. It willbe understood that while a particular carbon-based large capacitanceelectrode has been disclosed, for illustrative purposes only, any one ofa number of large capacitance electrode films/layers that would be knownto those with ordinary skill in the art having the present disclosurebefore them are likewise contemplated for use.

Electrochemical medium 124 may also comprise complexing agents, such as,but not limited to, pyridines; bipyridines, such as 2,2′-bipyridine;1,10-phenathrolines; imidazoles; crown ethers; polyethylene glycol;thiourea; halides, including chloride, iodide, and bromide; andtriphenylphosphine or other phosphine ligands—as well as those providedin the experiments infra. Such agents can cause the cathodic material tobecome more stable in a variety of solvents as well as shift thereduction potential toward more negative potentials, for example, in thecase of cationic silver, cathodic peak potential shifts of approximately0.5 volts (V) to approximately 1.0 V were observed in common solventssuch as propylene carbonate (PC), gamma-butyrolactone (GBL), andN,N-dimethyl formamide (DMF). These complexing agents have also beenreported to enhance the uniformity of deposition when the cathodicmaterial is deposited.

Electrochemical medium 124 may also comprise one or more redox buffers,color-stabilizers, and/or additives consistent with those disclosed inU.S. Pat. No. 6,188,505, U.S. Pat. No. 6,310,714, U.S. Pat. No.6,433,914, and/or U.S. application Ser. No. 10/208,525, all of which areentitled “Color-Stabilized Electrochromic Devices,” and all of which arehereby incorporated herein by reference in their entirety.

In addition, electrochemical medium 124 may comprise other materials,such as light absorbers, light stabilizers, thermal stabilizers,antioxidants, thickeners, viscosity modifiers, tint providing agents,and mixtures thereof. Suitable UV-stabilizers may include: the materialethyl-2-cyano-3,3-diphenyl acrylate, sold by BASF of Parsippany, N.Y.,under the trademark Uvinul N-35 and by Aceto Corp., of Flushing, N.Y.,under the trademark Viosorb 910; the material(2-ethylhexyl)-2-cyano-3,3-diphenyl acrylate, sold by BASF under thetrademark Uvinul N-539; the material2-(2′-hydroxy-4′-methylphenyl)benzotriazole, sold by Ciba-Geigy Corp.under the trademark Tinuvin P; the material3-[3-(2H-benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]propionic acid pentyl ester prepared from Tinuvin 213, sold byCiba-Geigy Corp., via conventional hydrolysis followed by conventionalesterification (hereinafter “Tinuvin PE”); the material2,4-dihydroxybenzophenone sold by, among many others, Aldrich ChemicalCo.; the material 2-hydroxy-4-methoxybenzophenone sold by AmericanCyanamid under the trademark Cyasorb UV 9; and the material2-ethyl-2′-ethoxyalanilide sold by Sandoz Color & Chemicals under thetrademark Sanduvor VSU—to name a few.

It will be understood that the anodic and cathodic materials are presentin the electrochemical medium in sufficient quantities such that thereversible electrodeposition device maintains a desired low transmissionstate. For illustrative purposes only, the anodic and cathodic materialsare present from approximately 0.005 weight percent to approximately 50weight percent, and more preferably from approximately 0.01 weightpercent to approximately 35 weight percent. While particular quantitiesof the anodic as well as cathodic materials have been provided, it willbe understood that the desired quantities may vary greatly dependingupon the geometric configuration of the chamber containingelectrochemical medium 124.

Without being bound to any one particular theory, it is believed that,unlike may prior art devices, the inclusion of excess anodic material indevices of the present invention inhibits undesirable oxidation of othercomponents, such as solvent, in the medium—which leads to devicedegradation. Similarly, the inclusion of a redox buffer inhibitsundesirable side reactions in the device.

Electrochemical medium 124 may comprise any one of a number of common,commercially available solvents, including 3-methylsulfolane; dimethylsulfoxide; N,N-dimethyl formamide (DMF); glymes, such asdi(ethyleneglycol) methylether, tetraglyme, and other polyethers;alcohols, such as ethoxyethanol, glycols, etcetera; nitrites, such asacetonitrile, glutaronitrile, 3-hydroxypropionitrile, and2-methylglutaronitrile; ketones, including 2-acetylbutyrolactone, andcyclopentanone; cyclic esters including beta-propiolactone,gamma-butyrolactone (GBL), and gamma-valerolactone; propylene carbonate(PC), ethylene carbonate; ionic liquids (See U.S. Pat. No.6,552,843—which is hereby incorporated herein by reference in itsentirety) and homogenous mixtures of the same. While specific solventshave been disclosed as being associated with the electrochemical medium,numerous other solvents that would be known to those having ordinaryskill in the art having the present disclosure before them are likewisecontemplated for use.

The electrochemical medium can also be gelled or comprise a crosslinkedpolymer matrix as is described in U.S. Pat. No. 5,679,283 entitled“Electrochromic Layer and Devices Comprising Same,” which is herebyincorporated herein by reference in its entirety.

The electrochemical medium may also comprise a polymer that may furtherinclude a plasticizer and may also include an inert salt. The polymermay be a commercially available polymer such as PEO, PVF, PVB, PMMA,etcetera. One example of a polymeric solid electrolyte medium isdisclosed in U.S. Pat. No. 6,361,709 B1 entitled “Optically TransparentPolymeric Solid Electrolyte,” which is hereby incorporated herein byreference in its entirety.

Electrodeposition as disclosed herein can be used in a wide variety ofapplications wherein the transmitted or reflected light can bemodulated. Such devices include rear-view mirrors for vehicles; windowsfor the exterior of a building, home or vehicle; skylights for buildingsincluding tubular light filters; windows in office or room partitions;display devices; variable reflectors—just to name a few.

The electrochemical media of the present invention utilize manydifferent materials, the preparation and/or commercially availablesources are provided herein, unless the material is well known in theart. It will be understood that, unless specified otherwise, thestarting reagents are commercially available from Aldrich Chemical Co.,of Milwaukee, Wis., Ciba-Geigy Corp., and/or other common chemicalsuppliers. It will be further understood that conventional chemicalabbreviations will be used when appropriate including the following:grams (g); milliliters (mL); moles (mol); millimoles (mmol); molar (M);millimolar (mM); pounds per square inch (psi); hours (h); and degreesCentigrade (° C.).

Preparation of (6-(tri-tert-butylferrocenyl)hexyl)triethylammoniumtetrafluoroborate

It will be understood that(6-(tri-tert-butylferrocenyl)hexyl)triethyl-ammonium tetrafluoroboratewas prepared in a generally analogous manner to(6-(tetra-tert-butylferrocenyl)hexyl)triethylammonium tetrafluoroborateas is disclosed in U.S. Pat. No. 6,188,505 with the following materialmodifications.

To a N₂ purged flask, filled with 500 mL of dichloroethane, 50 g of1,1′,3,3′-tetra(tert-butyl)ferrocene (Bu₄Fc) was added followed by 26.8g of 6-bromohexanoyl chloride dissolved in 100 mL of dichloroethane. 20g of AlCl₃ was added to the solution slowly enough that the temperaturecould be kept below about 30° C.-35° C. The reaction was continued untilonly trace amounts of starting Bu₄Fc were evident by thin layerchromatography using hexane as the eluent. The reaction was thenquenched by slowly pouring into water, with stirring. A sufficientquantity of diethyl ether was added to the stirring mixture to allow forphase separation, and zinc dust was added to convert any greenferrocinium species present in the aqueous layer to the organic solubleferrocene derivative. Once the aqueous layer was nearly colorless, thephases were separated and the aqueous layer was extracted with anotherportion of diethyl ether. The combined organic portions were then washedwith NaHCO₃ and brine, followed by drying over anhydrous MgSO₄. Afterfiltering the solution, the solvent was removed to leave a red oil. Thered oil was then washed with cold hexane to remove any residual Bu₄Fc,and the product (6-bromo-1-tri(tert-butyl)ferrocenyl-1-hexanone) wasisolated by chromatography on silica. The remaining synthesis of(6-(tri-tert-butylferrocenyl)-hexyl)triethylammonium tetrafluoroboratewere carried out in a generally analogous manner to that as is providedin U.S. Pat. No. 6,188,505 relative to the preparation of(6-(tetra-tert-butylferrocenyl)hexyl)triethylammonium tetrafluoroborate.

It will be further understood that the preparation of(6-(tri-tert-butylferrocinium)hexyl)triethylammonium tetrafluoroboratewas carried out in an analogous manner to that as is provided in U.S.Pat. No. 6,188,505 relative to the preparation of(6-(tetra-tert-butylferrocinium)hexyl)triethylammoniumtetrafluoroborate.

In support of the present invention, several experiments were conductedwherein the concentration of the anodic material was controllablyconfigured relative to the cathodic material, toward analyzing theelectrochemical performance of the electrodeposition devices. Inaddition, the electrochemical performance of the electrodepositiondevices having one or more redox buffers were compared toelectrodeposition devices void of the same.

In each one of the examples provided herein below, the electrodepositiondevices prepared were approximately 3″×3″ and fabricated from a firstpiece of glass (substrate) coated with ITO (sheet resistance ˜10 Ω/□)which was overcoated with a thin layer of platinum metal (25 Å). Thissubstrate was aligned with a piece of ITO coated glass (sheet resistance˜10 Ω/□) with the electrode surfaces facing each other with a perimeterseal and two holes drilled into the ITO coated glass plate forintroduction of the medium into the cell. All cycling tests involvedcontinuous switching between applied potentials of 0 V and 0.65 V. Onecycle consisted of 30 minutes at each applied potential.

Experiment No. 1

In this experiment two electrochemical media were prepared by mixing thefollowing materials together in the concentrations provided below. Onceprepared, the electrochemical media were incorporated into theelectrodeposition devices for testing disclosed supra: ComponentMaterial Concentration Cathodic Silver triflate 0.15M Anodic(6-(tri-tert-butylferrocenyl)hexyl)triethyl- 0.15M ammoniumtetrafluoroborate Solvent DMF — Complexing 2,2′-bipyridine  1.5M Agent

Experiment No. 1A

Component Material Concentration Cathodic Silver triflate  0.08M Anodic(6-(tri-tert-butylferrocenyl)hexyl)triethyl-  0.08M ammoniumtetrafluoroborate Solvent DMF — Complexing 2,2′-bipyridine  1.0M AgentRedox (6-(tri-tert-butyl- 0.012M Bufferferrocinium)hexyl)triethylammonium tetrafluoroborate

Experiment No. 1B

Both devices exhibited a yellow to green-yellow color and had a whitelight transmission of 52%. A uniform bright silver film was observed forboth devices when 0.6-0.7 V was applied with a white light transmissionof less than 1%. The devices were cycled at 0.65 V for 360 cycles. Aftercycling, device (1A) exhibited a hazy deposit that would not completelydissolve even after 4 days which caused the transmission in the bleached(0 potential, open circuit) state to decrease from 52% to 48% aftercycling. In comparison, device (1B) was clear with no residual depositsand the bleached state transmission remained at 52%—even after 1,338cycles. As such, Experiment No. 1 verifies that the addition of a redoxbuffer to an electrochemical medium materially enhances theelectrochemical performance of an associated electrodeposition device,relative to an electrodeposition device having anodic and cathodicmaterials of the same concentration.

Experiment No. 2

In this experiment two electrochemical media were prepared by mixing thefollowing materials together in the concentrations provided below. Onceprepared the electrochemical media were incorporated into theelectrodeposition devices for testing disclosed supra:

Experiment No. 2A

Component Material Concentration Cathodic Silver triflate 0.08M AnodicTEAPphen* 0.15M Solvent GBL — Complexing Br⁻ (as the tetrabutyl- 0.17MAgent ammonium salt) Complexing 2,2′-bipyridine 0.08M Agent*See U.S. application Ser. No. 10/283,506 for preparation

Experiment No. 2B

Component Material Concentration Cathodic Silver triflate  0.08M AnodicTEAPphen*  0.15M Solvent GBL — Complexing Br⁻ (as the tetrabutylammoniumsalt)  0.17M Agent Complexing 2,2′-bipyridine  0.08M Agent Redox BufferA Decamethyl ferrocene** 0.005M Redox Buffer B Decamethyl ferrocinium0.005M tetrafluoroborate***See U.S. application Ser. No. 10/283,506 for preparation**See U.S. Pat. No. 6,392,783 for preparation

The addition of the ferrocene/ferrocinium redox buffer caused the devicewith medium 2B to show superior durability when devices 2A and 2B werecycled at 0.65V. After 750 cycles device 2A showed large areas of theelectrode where the silver film did not completely erase. In comparison,device 2B promptly returned to its high transmittance state after theelectrical potential was removed.

Experiment No. 3

In this experiment two electrochemical media were prepared by mixing thefollowing materials together in the concentrations provided below. Onceprepared the electrochemical media were incorporated into theelectrodeposition devices for testing disclosed supra:

Experiment No. 3A

Component Material Concentration Cathodic Silver triflate  0.15M AnodicTEAPphen*  0.15M Solvent PC — Complexing Br⁻ (as the tetrabutylammoniumsalt)  0.35M Agent Redox Buffer Decamethyl ferrocene** 0.010M*See U.S. application Ser. No. 10/283,506 for preparation**See U.S. Pat. No. 6,392,783 for preparation

Experiment No. 3B

Component Material Concentration Cathodic Silver triflate 0.08M AnodicTEAPphen* 0.15M Solvent GBL — Complexing Br⁻ (as the  0.2M Agenttetrabutylammonium salt) Redox Buffer Decamethyl ferrocene** 0.01M*See U.S. application Ser. No. 10/283,506 for preparation**See U.S. Pat. No. 6,392,783 for preparation

Device 3A exhibited silver deposition beginning with an applied voltageof approximately 0.4V however at higher potentials of 0.6V the depositsbecame non-uniform. In contrast, device 3B produced a thick uniformsilver deposit starting at 0.4V and the silver deposit remained uniformat 0.6V—thus indicating that excess anodic material in solutionincreases the stability of the deposited metal film.

Experiment No. 4

In this experiment one electrochemical medium was prepared by mixing thefollowing materials together in the concentrations provided below. Onceprepared the electrochemical medium was incorporated into theelectrodeposition devices for testing disclosed supra:

Experiment No. 4

Component Material Concentration Cathodic Silver triflate  0.08M AnodicTEAPphen*  0.15M Solvent DMF — Complexing Br⁻ (as the tetrabutylammoniumsalt)  0.20M Agent Redox Buffer A Decamethyl ferrocene** 0.005M RedoxBuffer B Decamethyl ferrocinium 0.005M tetrafluoroborate***See U.S. application Ser. No. 10/283,506 for preparation**See U.S. Pat. No. 6,392,783 for preparation

Device 4 exhibited a high transmittance state with 62% white lighttransmittance and a low transmittance state of 4%. The device was cycledbetween the high and low transmittance states for 4 weeks (600 cycles)with no appreciable change in its characteristics.

It has also been discovered that when a device of the present inventionis held in its low transmission or reflective state for long periods oftime, the measured current can increase which can result in any one of anumber of adverse conditions such as, electrochemical mediumdegradation, dendrite formation at or near the nucleation layer,non-uniform plating—just to name a few. In has been found that theapplication of a voltage of lower magnitude (i.e. a maintenancepotential) maintained a device in its low transmission state, and alsothe current passed, for extended periods. By way of example, a devicemade using trimethylhydroquinone as the anodic material can be madereflective with the application of approximately 0.7 V (i.e. atransitional potential) and after approximately one minute, the voltagecan be reduced to a value of approximately 0.3-0.4 V (i.e. a maintenancepotential) while the device maintains the same level of transmission andcurrent.

While the invention has been described in detail herein in accordancewith certain preferred embodiments thereof, many modifications andchanges therein may be effected by those skilled in the art.Accordingly, it is our intent to be limited only by the scope of theappending claims and not by way of details and instrumentalitiesdescribing the embodiments shown herein.

1. A reversible electrodeposition device, comprising: a first electrodecomprising a first substrate having an electrically conductive materialassociated therewith; a second electrode comprising a second substratehaving an electrically conductive material associated therewith, whereinthe second electrode comprises at least one of the group comprising anelectronically conducting polymer layer, a sol-gel layer, a redoxpolymer layer, an electroactive layer, a surface attached layer; a largecapacitance layer, and a metal oxide layer; a nucleation layer at leastpartially covering at least one of the electrically conductive materialsof the first and second substrates; and an electrochemical mediumcontained within a chamber positioned between the first and secondsubstrates which comprises a cathodic electroactive material.
 2. Thereversible electrodeposition device according to claim 1, furthercomprising a redox buffer.
 3. The reversible electrodeposition deviceaccording to claim 2, wherein the redox buffer is more easily reducedthan the cathodic material.
 4. The reversible electrodeposition deviceaccording to claim 2, further comprising a solution phase anodicelectroactive material.
 5. The reversible electrodeposition deviceaccording to claim 4, wherein the concentration of the anodicelectroactive material is greater than the cathodic electroactivematerial, to, in turn, enhance the electrochemical performance of theelectrodeposition device.
 6. The reversible electrodeposition deviceaccording to claim 4, wherein the redox buffer is more easily oxidizedthan the anodic material.
 7. The reversible electrodeposition deviceaccording to claim 6, wherein the redox buffer comprises: a firstcomponent that is more easily reduced than the cathodic material; and asecond component that is more easily oxidized than the anodic material.8. The reversible electrodeposition device according to claim 1, whereinthe cathodic material comprises a salt of an active metal.
 9. Thereversible electrodeposition device according to claim 2, wherein theredox buffer is present in a range from approximately 0.005 weightpercent to approximately 5 weight percent.
 10. The reversibleelectrodeposition device according to claim 1, wherein theelectrochemical medium further comprises a complexing agent.
 11. Thereversible electrodeposition device according to claim 10, wherein aredox buffer is more easily reduced than the cathodic material.
 12. Thereversible electrodeposition device according to claim 10, furthercomprising a solution phase anodic electroactive material.
 13. Thereversible electrodeposition device according to claim 12, wherein aredox buffer is more easily oxidized than the anodic material.
 14. Thereversible electrodeposition device according to claim 13, wherein theredox buffer comprises: a first component that is more easily reducedthan the cathodic material; and a second component that is more easilyoxidized than the anodic material.
 15. The reversible electrodepositiondevice according to claim 10, wherein a redox buffer is present in arange from approximately 0.005 weight percent to approximately 5 weightpercent.
 16. The reversible electrodeposition device according to claim10, wherein the device is a window.
 17. A reversible electrodepositionwindow having a non-patterned electrode, comprising: a first electrodecomprising a first substrate having an electrically conductive materialassociated therewith; a second, non-patterned electrode comprising asecond substrate having an electrically conductive material associatedtherewith, wherein the second substrate is associated with at least oneof the group comprising an electronically conducting polymer layer, asol-gel layer, a redox polymer layer, an electroactive layer, a surfaceattached layer; a large capacitance layer, and a metal oxide layer; anucleation layer at least partially covering the electrically conductivematerial of the first substrate; and an electrochemical medium containedwithin a chamber positioned between the first and second substrateswhich comprises a cathodic electroactive material.
 18. The reversibleelectrodeposition window according to claim 17, wherein theelectrochemical medium further comprises a redox buffer.
 19. Thereversible electrodeposition device according to claim 18, wherein theredox buffer is present in a range from approximately 0.005 weightpercent to approximately 5 weight percent.
 20. The reversibleelectrodeposition window according to claim 18, wherein the redox bufferis more easily reduced than the cathodic material.
 21. The reversibleelectrodeposition device according to claim 17, further comprising asolution phase anodic electroactive material.
 22. The reversibleelectrodeposition window according to claim 21, wherein the redox bufferis more easily oxidized than the anodic material.
 23. The reversibleelectrodeposition window according to claim 21, wherein the redox buffercomprises: a first component that is more easily reduced than thecathodic material; and a second component that is more easily oxidizedthan the anodic material.
 24. The reversible electrodeposition windowaccording to claim 17, wherein the electrochemical medium furthercomprises a complexing agent.
 25. A reversible electrodeposition devicehaving a non-patterned electrode, comprising: a first electrodecomprising a first substrate having an electrically conductive materialassociated therewith; a second, non-patterned electrode comprising asecond substrate having an electrically conductive material associatedtherewith; an electrochemical medium contained within a chamberpositioned between the first and second substrates; wherein uponapplication of a transitional potential, the reversibleelectrodeposition device transitions form a high transmission state to alow transmission state; and wherein upon application of a maintenancepotential lower than the transitional potential, the reversibleelectrodeposition device maintains the low transmission state.